This invention relates to a freon gas detecting element for detecting the presence of freon gas.
Freon gas is used as coolant for cooling apparatus such as electric refrigerators, air conditioners and the like. Leak of the freon gas from the cooling apparatus worsens cooling ability. Therefore leak of the freon gas has to be detected by a device having high stability and high detecting sensitivity.
There are known two types of freon gas leak detectors as described, for example, in a paper entitled "Halogen Leak Test" by Takeo Tsuchiya, Journal of the Vacuum Society of Japan, Vol. 22. No. 2, 1979. One is a cation emission type leak detector, and the other is a electric discharge halogenated hydrocarbon gases type leak detector. The cation emission type leak detector comprises a cylindrical ion collector (cathode) made of Pt, and an anode inside the cylindrical ion collector which is made of ceramics including substantial amounts of an alkali element such as Na or K. The anode is provided with a filament made of Pt wound around the outer periphery thereof and heated to about 800.degree. C. by passing current through the filament. When the freon gas comes between the anode and the ion collector, the high temperature alkali, such as Na or K, on the surface of the ceramics exchanges electrons with the haloid compound which has strong electron affinity. As the result, cations of Na.sup.+ and K.sup.+ are produced and flow into the ion collector. The leaking freon gas, thereby, can be detected.
However, it is difficult for the freon gas detector of this type to be miniaturized because it must be provided with a heating mechanism for heating the ceramics to high temperature (800.degree. C.). Also, the stability and detecting sensitivity are inadequate. Particularly, a large quantity of Na.sup.+ or K.sup.+ is released from the surface of the ceramics when substantial amounts of freon gas are leaking. As a result, the detecting sensitivity is low until the element recovers. Further, the reliability of the detector is not sufficient because the detector is also sensitive to other gas besides freon gas.
On the other hand, the electric discharge halogenated hydrocarbon gases type leak detector is provided with a pair of needle electrodes facing each other with a gap therebetween. To the electrodes is applied a high voltage (0.8-2 K) for producing a silent discharge at the gap. When the freon gas comes into the gap, the discharge is interrupted. As a result, the freon gas is detected.
Further, in a detector of this type, high voltage has to be applied and the amount of freon gas can not be measured quantitatively. In addition, the discharge may be interrupted by other causes besides freon gas, for example, wind. Therefore the reliability of the detector is not sufficient.